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Researchers were inspired by a certain purple villain to study the physics of finger snapping, and they found that the mundane hand motion is actually quite an impressive feat.

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Sources:
https://royalsocietypublishing.org/doi/10.1098/rsif.2021.0672#d1e741
https://www.sciencenews.org/article/finger-snap-physics-new-high-speed-video-thanos
https://www.eurekalert.org/news-releases/934621

Image Sources
https://www.istockphoto.com/photo/african-oversized-woman-clicking-fingers-standing-posing-on-blue-background-gm1297644806-390727243
https://rs.figshare.com/collections/Supplementary_material_from_The_ultrafast_snap_of_a_finger_is_mediated_by_skin_friction_/5683810
https://www.istockphoto.com/photo/baseball-pitcher-on-stadium-gm522537732-91676159
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https://commons.wikimedia.org/wiki/File:Rhynchotermes_(10.3897-zookeys.892.38743)_Figure_3.jpg
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A snap of the fingers is a metaphor for something easy, like you could do it in a snap, but researchers who really buckled down to study the physics of finger snapping found it's actually a pretty impressive feat, and understanding it could help us study things from insect jaws to prosthetics.

In a study published in 2021 in the Journal of the Royal Society Interface, researchers figured out the physics of the finger snap using high-speed cameras and force sensors. The inspiration for the study came after seeing a movie where the villain snaps his fingers while wearing a metal glove. Six guesses for which one that is. The researchers wondered whether it would actually be possible to do that snap, because the metal wouldn't have much friction.

Well, according to the study, the perfect snap can be broken down into three phases. The first is loading, where the thumb and middle finger store up kinetic energy, or energy of motion. Then comes the unlatching, where the fingers start to slide past one another. And finally, unlatching movement is when the fingers move at ultra fast speeds until the middle finger hits the palm, creating shock waves that make the snap sound.

The whole thing happens in less than seven milliseconds, 20 times faster than the blink of an eye, and during that unlatching movement phase, your fingers are rotating at up to 7800 degrees per second - almost as fast as a professional baseball player rotates their arm during a pitch. All this means finger snapping is one of the fastest, most explosive movements our bodies can muster.

But whether those three phases add up to a snap or silence comes down to one key element: friction. Friction is the resistance between two objects moving over one another, and it turns out that snapping requires a sort of Goldilocks zone of friction. You see, you want friction to help build up the kinetic energy in the loading phase, but you have to overcome the friction when it comes time to release during unlatching.

Researchers figured out just how much friction contributes to snapping by rigging how slippery and squishy a person's fingers were. To make them more slippery, participants in the study wore lubricated nitrile gloves, and when they did, their fingers didn't create enough friction, and they could not store up enough energy for a forceful and loud snap. If their fingers were instead made more grippy by wearing a latex rubber glove, then participants couldn't release their fingers, and the snap also flopped.

The researchers also wanted to see whether the squishiness of someone's fingers, or how compressible they were, had anything to do with the friction that built up, so some participants wore a hard metal thimble with a nitrile glove on top, and it turns out fingers need to be at least a little squishy to help build up that friction. So snapping with a metal glove on, not possible for people, maybe possible if you have Infinity Stones or something.

The researchers, who had previously studied super fast motion in other animals, took all this information and combined it into a mathematical model that could now be used to help in other fields of science. For example, it could help biologists understand the snaps of, say, Panamanian termite soldiers. Those are insects that snap their jaws together ultra fast to defend their hive, and the researchers propose the mechanism might be similar to finger snapping. Plus, understanding the dynamics of the finger snap could help engineers fine tune the movement of prosthetics, which you gotta say isn't just fun but pretty snappy research, indeed.

It's funny how we don't really understand things like finger snapping until someone goes, "But how does that actually work?," and they decide to do some science about it. But to learn more about the physics of the everyday, from bridges to fridges, you might like Brilliant's course Physics of the Everyday or any one of the math, science, engineering, and computer science courses they have available.

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